The aliens are a cross of Daleks and Wellsian Martians. The landmarks they are stalking are supposed to be models in Mini-Europe. They are: Big Ben in London, Acropolis in Athens, Stift Melk in Austria, Brandenburger Tor in Berlin, the Sacré-Coeur on Montmartre and the Arc de Triomphe in Paris. The whole episode was supposed to look like TV news, hence the scanlines.